When a hydraulic fluid delivered from one hydraulic pump is supplied to a plurality of actuators, the hydraulic fluid is supplied only to the actuator having a lower load pressure and thus as a proposal for dissolving the problem, there has been known a hydraulic circuit disclosed in JP, A 60-11706, for example. This hydraulic circuit is shown in FIG. 6.
In FIG. 6, a delivery line 102 of a hydraulic pump 101 is connected to actuators 106, 116 via a valve unit 150. The valve unit 150 comprises pressure compensating valves 103, 113, hold check valves 104a, 114a, directional control valves 105, 115, and a shuttle valve 107. The pressure compensating valves 103, 113 are connected in parallel to the delivery line 102, and the directional control valves 105, 115 are respectively connected to outlet lines 104, 114 of the pressure compensating valves 103, 113 through the hold check valves 104a, 114a and outlet sides of the respective directional control valves 105, 115 are respectively connected to the actuators 106, 116. The pressure compensating valves 103, 113 are configured to be urged in their opening directions by a delivery pressure of the hydraulic pump 101 and outlet pressures of the directional control valves 105, 115 and to be urged in their closing directions by inlet pressures of the directional control valves 105, 115 and the highest load pressure. The shuttle valve 107 compares the load pressures of the actuators 106, 116 to select the higher one thereof to supply the same to the pressure compensating valves 103, 113 and a load sensing valve 120. With such a circuit structure, when the plurality of the directional control valves 103, 113 are operated simultaneously, a hydraulic fluid delivered from the hydraulic pump 101 is supplied to the respective actuators 106, 116 at a predetermined distribution ratio by the function of the pressure compensating valves 103, 113.